Double-walled chimneys are known in the art, one example of which is disclosed in the U.S. Pat. 3,902,744 to Stone and prior art cited therein. The basic construction involves inner and outer concentric pipes affording an annular insulating space between them. Fundamentally, the assembly or erection of the chimney proceeds with coaxial, end-to-end stacking of, say, a pair of inner pipes, the meeting ends of which are radially outwardly flanged to receive an inner annular ring which clamps the pipes together. An outer lower pipe surrounds the lower of the inner pipes and its upper end stops axially short of the junction between the inner pipes. An upper outer pipe is assembled from above and its lower end stops above and axially short of the inner piipe junction, the space or gap between the proximate ends of the outer pipes exposing or opening to the inner band. It is in this area that spacing means is most advantageously employed, not only to space the outer pipes from the inner pipes but also to stabilize the outer pipes axially preparatory to the attachment of an outer band around the outer pipes which functions to secure the outer pipes together and to close the gap and thus to complete the insulating space between the pipes.
In one form of the prior art, the spacers are affixed to the interior of the outer pipes and extend inwardly and axially to be received or embraced by the band for the inner pipes. This type of installation requires a degree of care in seeing that the inner band be subsequently tightened to secure the spacers. Since there are several such spacers, considerable time is required to make the proper assembly.
According to the present invention, the spacers are affixed to the inner band and are projectable into proper relationships to the outer pipes with a minimum of attention. A further feature is that the inner band may be tightened before the assembly of the upper outer pipe. Still further, the spacers are pivoted to the inner bands on axes radial to the band and may be turned about their pivots to facilitate installation, besides which the pivoting enables turning of the spacers to lie generally along the periphery of the band so as to contribute to easy handling, packing and shipping.
Further features will become apparent as preferred embodiments of the invention are disclosed in detail in the ensuing description and accompanying sheets of drawings.